The corruption scandals that have finally engulfed Ehud Olmert's premiership erupted on May 9 as Israel was celebrating its 60th birthday.

The allegations first involved suspicions that Olmert had been receiving hundreds of thousands of dollars from US millionaire financier and political donor Morris Moshe Talansky, and possibly other foreigners.

But as investigations continued, allegations widened to include claims that Olmert defrauded charities and other non-government organisations, including the Holocaust Museum and an institution for people with mental disabilities, by submitting expense claims for which he had already been reimbursed.

Olmert has repeatedly denied any wrongdoing, but as this is the fifth time Olmert has been investigated for corruption since replacing Ariel Sharon as prime minister in 2006, he has been under intense pressure to resign.

The police have interviewed dozens of witnesses including executives and employees of the various non-profit agencies. They have also raided the offices of travel operator, Rishon Tours and confiscated documents.

Olmert has allegedly told investigators that his family's trips were funded through the use of flight credits, or points, accrued and credited to him by several airlines. But the police allege Olmert did not accumulate enough points to cover all the trips.

The police are now investigating Olmert for a string of offences including serious fraud unlawfully receiving money.

The initial allegations date back to 1993 when Olmert first ran to be Jerusalem's mayor and later when appointed as minister of industry, trade and labour in Sharon's government. Olmert's chief of staff, Shula Zaken, who was placed under house arrest, and lawyer Uri Messer, were also embroiled.

Talansky, a long-time supporter and friend of Olmert, told investigators that he gave at least $150,000 (£75,000) over 15 years, to the prime minister.

There are no records of how the money was spent and Talansky said he was "disturbed" when Olmert specifically asked for cash rather than cheques. Talansky's generosity also extended to purchasing cigars and expensive pens.

More recently, police began investigating claims that Olmert sought multiple funding for foreign trips and banked the surplus. Investigators have alleged that the money was deposited in a private bank account, which was handled by a travel agency. These funds were then allegedly used to pay for private trips abroad for Olmert and his family.

Police say Olmert amassed close to $100,000 in the private bank account.